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Re: *newbie* output of ScalarTripleProduct

  • To: mathgroup at smc.vnet.net
  • Subject: [mg106772] Re: *newbie* output of ScalarTripleProduct
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Sat, 23 Jan 2010 07:32:08 -0500 (EST)

On 1/22/10 at 5:41 AM, marco.fax at email.it (pippo) wrote:

>I'm (almost) new to mathematica ... I coped this from some tutorial

>Needs["VectorAnalysis`"]
>r1 = {1, -3, 2}
>r2 = {3, 7,-5}
>r3 = {4, 1, 6}
>r={x,y,z}
>ScalarTripleProduct[r-r1,r2-r2,r3-r1]==0

>the output i get is: Out[6]= True

>What am I missing ?

What where you expecting? The middle argument given to
ScalarTripleProduct is r2-r2 which is clearly {0,0,0}. If any
one of the three vectors is {0,0,0} the triple scalar produce
will be zero. So, Mathematica has correctly reported the
computed triple scalar product equals 0.



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